One eyeball protruding and one not protruding may be related to trauma, or it may be caused by eye tumors, hyperthyroidism and other reasons. 1. Trauma: In daily work or life, if one eye is suddenly hit by external force, resulting in intraorbital hematoma or intraorbital fracture, it may cause protrusion of the eyeball on the injured side, which will result in protruding of one eyeball and non-protruding of the other. 2. Eye tumor: due to the presence of some kind of cell overproliferation in the eye, eye tumor is induced. If only one side of the eyelid suffers from tumor, it may cause one eyeball protruding and one eyeball not protruding, and it may be accompanied by eye swelling, congestion, pain and other uncomfortable symptoms. 3. Hyperthyroidism: This disease leads to excessive secretion of thyroid hormone, which can easily cause hyperplasia of extraocular muscles, resulting in damage of eye tissues, thus causing eyeball protrusion of the patient, which is mostly seen in both eyes, and if one eye is obvious, the patient will have one eyeball protruding and the other one protruding is not obvious. It is recommended that patients with obvious eyeball protrusion should consult a doctor in time to assess their condition and follow the doctor’s instructions for treatment.